Methods and apparatus for supporting session registration messaging

ABSTRACT

Session signaling register message transmission methods and apparatus well suited for use in a communication system which supports mobile nodes capable of moving between domains and access nodes in a domain are described. Broadcasting of session signaling register messages is supported to reduce the number of registration messages which need to be transmitted between a mobile node and an access node. A paging and location server is used to reduce the number of session signaling register messages transmitted between domains. A visiting node registers with a paging and location server. The session signaling address of the paging and location server being used by a visiting mobile node is registered with the visiting node&#39;s home session signaling server. As the visiting node moves between access nodes in the visited domain the paging and location server it uses remains the same eliminating the need to update the home session signaling servers.

RELATED APPLICATIONS

The present application is a continuation-in-part of U.S. patentapplication Ser. No. 10/167,668, filed Jun. 11, 2002 now U.S. Pat. No.6,970,445, which is titled “Methods and Apparatus For Supporting SessionSignaling And Mobility Management in A Communications System” whichclaims the benefit of the following applications: U.S. ProvisionalPatent Application Ser. No. 60/298,283, filed on Jun. 14, 2001, titled“Location of SIP Proxy Server in Wireless Access Router”; U.S.Provisional Patent Application Ser. No. 60/369,016, filed on Apr. 1,2002, titled: “Methods and Apparatus for Registration for SIP Servicesin Mobile Networks”; U.S. Provisional Patent Application Ser. No.60/370,524, filed on Apr. 5, 2002, titled: “Methods and Apparatus forSIP Message Forwarding and Redirection”; and U.S. Provisional PatentApplication Ser. No. 60/313,035, filed on Aug. 16, 2001, titled: “AMethod for Controlling IP Applications During Network Changes thatResult in Resource Shortages”, each of the above mentioned patentapplications is hereby expressly incorporated by reference.

FIELD OF THE INVENTION

The present invention is directed to methods and apparatus forestablishing a data communication session and, more particularly, tomethods and apparatus for establishing a data communication sessionthrough an access node in a multi-node network, e.g., a cellular networkin which mobile end systems communicate with each other and other endsystems through access nodes.

BACKGROUND

Internet Protocol (IP) technology is designed to enable packet-switchedinterconnection of a heterogeneous set of computers and communicationnetworks. A potentially diverse set of network and link layertechnologies are interconnected through nodes, e.g., gateways (orrouters), that provide a packet forwarding service. Information istransferred between end nodes (or hosts) as blocks of data calleddatagrams, where source and destination hosts are identified by fixedlength addresses. Routing in IP internetworks is connectionless innature, in that datagrams are forwarded between routers on a hop-by-hopbasis using the destination address in the datagram.

Mobile IP (Ref: IETF RFC 2002) enables an IP host, also called a “mobilenode” in the context of Mobile IP, to dynamically change its point ofattachment to the network, yet remain contactable via a previously given“home address”. To achieve this a temporary local address or “care ofaddress” is associated with the mobile node when it visits a foreignnetwork. In some cases the care of address is that of a “foreign agent”that assists in this process, while in other cases the care of addressmay be directly assigned to the mobile node. The care of address isregistered back on the home network in a node referred to as the “homeagent”. The home agent intercepts packets destined to the home addressof the mobile node and redirects the packets, by means of encapsulationand tunneling, towards the care of address associated with mobile nodein the visited network. Upon delivery to the care of address, theencapsulation is removed and the original packet destined to the homeaddress is delivered to the mobile node.

The Session Initiation Protocol (SIP) (Ref: IETF RFC 2543) enables endnodes or users to establish data communication sessions. SIP is aclient/server protocol consisting primarily of request and responsemessage exchanges. A SIP transaction typically comprises arequest/response pair. SIP uses application layer routing, wherein SIPmessages sent between two “user agents” may traverse throughintermediate processing nodes referred to as SIP servers. SIP useragents and servers determine the next SIP node to which each messageshould be directed based on inspection and processing of SIP messageheader fields. Once the next SIP node is determined, the message isforwarded to that SIP node using normal network layer routingmechanisms. An enterprise network or Internet Service Provider may useSIP servers to assist in session establishment, enforce policies, orsupport user agent mobility. SIP mobility support mechanisms allow auser agent to maintain reachability by registering its present locationinformation with a SIP server in its home network. This locationinformation could either identify the location of the user agent oranother SIP server to which request for the user agent should be sent(e.g., a SIP server in a visited network). The SIP server in the homenetwork can then route any request for the user agent based on thepresently registered location information.

Both a mobility management mechanism and a session establishmentmechanism are required to support services such as Voice over IP in acellular data network. FIG. 1 illustrates a system 100 based on a simplecombination of Mobile IP and SIP. The system 100 is not necessarilyprior art, but is useful for explaining Mobile IP and SIP for backgroundpurposes and therefore will be discussed here. The depicted system 100comprises a plurality of access nodes 114, 126, where each access node114, 126 provides connectivity to a plurality of N end nodes (160, 162),(164, 166), respectively, via corresponding access links (118, 120),(122, 124), respectively.

Interconnectivity between the access nodes 114, 126 is provided throughnetwork links 106, 108 and an intermediate network node 102. The networkalso includes a SIP server node 112 that is connected to theintermediate network node 102 by network link 110. The intermediatenetwork node 102 also provides interconnectivity to another network 128via network link 104, where the network 128 is the home network of endnode X 162. The home network 128 includes a Mobile IPv4 home agent node130 and a home SIP server node 132, each of which is connected to anintermediate network node 138 by one of two network links 134, 136,respectively. The intermediate network node 138 in the home network 128also provides interconnectivity to network nodes that are external fromthe perspective of the home network 128 via network link 104. In theillustrated system 100, SIP servers 112 and 132 are physically distinctand remotely located from access nodes 114, 126 requiring externalsignaling between the housing of servers 112, 126 whenever either of theservers needs to interact with an access node 114, 126. As a result ofthe locations of server 112, 132 relative to access nodes 114, 126undesirable delays may occur when a SIP server 112, 132 needs tointeract with the elements of one of the access nodes 114, 126.

In the depicted system 100, end node X 162 uses Mobile IP to maintainreachability, while its present point of attachment to the network isthrough visited access node 114. End node X 162 has registered theaddress associated with a Mobile IPv4 foreign agent module 116 of theaccess node 114 as a care of address with its home agent 130 in its homenetwork 128.

End node X 162 has also registered the location of a visited SIP server112 with its home SIP server node 132 in its home network 128. Thus, thehome SIP server 132 will direct SIP requests for end node X 162 to thevisited SIP server 112. The dashed arrows show the path of a SIP requestand response for a session initiated from end node Y 166 to end node X162. End node Y 166 directs the initial request message 140 to the homeSIP server 132 of end node X 162. The home SIP Server 132 subsequentlydirects a request message 142 to the visited SIP server 112 inaccordance with the registered location information. Following receptionof the request message 142 from the home SIP server 132, the visited SIPserver 112 directs a request message 144 to the home address of end nodeX 162. This request message 144 is forwarded via normal network routingall the way back to the home network 128 of end node X 162, where it isintercepted by the home agent 130. The home agent 130 encapsulates theintercepted request message 144 and tunnels the encapsulated requestmessagel46 to the foreign agent 116. Following reception of theencapsulated request message 146, the foreign agent 116 directs arequest message 148 to end node X 162.

Following reception of the request message 148, end node X 162 sends aresponse to end node Y 166 such that the response traverses backwardsthrough the same set of SIP intermediate servers that processed therequest. This is accomplished in part by the fact that the informationidentifying the SIP servers 132, 112 through which the request traversedwas added to the request message 142, 144 as it was forwarded. Thus, endnode X 162 initially directs a response message 150 to the visited SIPserver 112. The visited SIP Server 112 subsequently directs a responsemessage 152 to the home SIP server 132. Following reception of theresponse message 152 from the visited SIP server 112, the home SIPserver 132 directs a response message 154 to end node Y 166. However,the path of the response would be more circuitous in the case whereMobile IP operates in reverse tunneling mode (Ref: IETF RFC 2344).Although the alternate response signaling path is not shown in thefigure, the following briefly describes the case when reverse tunnelingis used. As opposed to being delivered directly to the visited SIPserver 112, the response sent from end node X 162 would be encapsulatedand tunneled to the home agent 130, where it would be decapsulated bythe home agent 130 and directed back to the visited SIP server 112. Thenfrom the visited SIP server 112, the SIP response signaling path wouldproceed as before, to the home SIP server 132, and finally to end node Y166.

The depicted system 100 clearly illustrates the inefficient andcircuitous forwarding of SIP request/response signaling associated withthe establishment of a data communication session between end node Y 166and end node X 162. System 100 also has several other deficiencies,particularly regarding session admission control, resource allocation,and mobility support. The primary difficulty with session admissioncontrol stems from the fact that the admission control and policydecision points do not coincide with the admission control and policyenforcement points. In particular, while the SIP servers 112, 132process session establishment signaling and effectively serve asadmission control and policy decision points, these servers 112, 132 arenot on the path of session data traffic, and thus cannot be admissioncontrol and policy enforcement points. Note that data session trafficwill not go through servers 112, 132 since these are only used forsession signaling. Furthermore, since the SIP servers 112, 132 are noton the data path, they may be easily bypassed by the session signalingtraffic provided that there are no additional control mechanisms.Admission control and policy enforcement can more effectively be appliedin the access nodes 114,126, but this would require additional signalingbetween the SIP servers 112, 132 and the access nodes 114, 126 andgreatly increase the complexity of the system 100. Similarly, withrespect to resource allocation, since the SIP servers 112, 132 are noton the data path, the admission control decision cannot easily accountfor the availability of system resources to support the requested datacommunication session.

In a wireless communication system, information regarding theavailability of resources at the access node 114, 126 and over theaccess links 118, 120, 122, 124 can be critical. Incorporation of accessnode and link resource availability information in the admission controldecision in the system 100 would again require additional signalingbetween the SIP servers 112, 132 and the access nodes 114, 126 and againgreatly increase the complexity of the system 100. Finally, supportingmobility in combination with all of the above signaling requiresadditional mechanisms to accommodate the movement of an end node 160,162, 164, 166 during session establishment. In addition to increasingthe complexity of the system 100, the use of additional signalingbetween the SIP servers 112, 132 and the access nodes 114, 126 toaddress these issues would also increase the latency associated withestablishment of a data communication session and increase the bandwidthutilization on network links, thus reducing the practicality of theresultant system.

In view of the above discussion, it is apparent that there is a need forimproved methods and apparatus for supporting end node mobility,communication session establishment and several other operations relatedto establishing and maintaining communications sessions in systems whichuse packets to transmit data.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates one technique for using Session Initiation Protocolsignaling in a mobile IP environment wherein a first mobile end nodeinteracts with another end node via various other network elements.

FIG. 2 illustrates an access node implemented in accordance with thepresent invention.

FIG. 3 illustrates a network diagram of a communications systemimplemented in accordance with an exemplary embodiment of the invention.

FIG. 4 illustrates signaling performed in the exemplary system shown inFIG. 3 as part of the processes of initiating and conducting a datacommunication session between a first mobile end node and another endnode in accordance with an exemplary embodiment of the invention.

FIGS. 5 and 6 illustrate signaling performed in the exemplary systemshown in FIG. 3 as part of the process of initiating and conducting adata communication session between a first mobile end node and anotherend node in accordance with an exemplary embodiment of the invention,while the first mobile end node is in the process of a handoff betweentwo access nodes.

FIG. 7 illustrates a multi-domain network diagram of a communicationssystem implemented in accordance with an exemplary embodiment of theinvention.

FIG. 8 illustrates a network diagram of a communications systemimplemented in accordance with an exemplary embodiment of the inventionthat includes a Paging and Location Server.

FIG. 9 is a simplified version of the exemplary system shown in FIG. 7that illustrates signaling performed for the purpose of end noderegistration to a home session signaling server via an access node.

FIG. 10 is a simplified version of the exemplary system shown in FIG. 7that illustrates signaling performed for the purpose of end noderegistration to multiple home session signaling servers via an accessnode by means of an aggregated registration.

FIG. 11 is a simplified version of the exemplary system shown in FIG. 8that illustrates signaling performed for the purpose of end noderegistration to a home session signaling server via chained registrationto an access node and a paging and location server.

FIG. 12 is a simplified version of the exemplary system shown in FIG. 8that illustrates signaling performed for the purpose of end noderegistration to a home session signaling server via parallelregistration to an access node and a paging and location server.

FIG. 13 is a simplified version of the exemplary system shown in FIG. 8that illustrates signaling performed for the purpose of end noderegistration to a paging and location server during a handoff operation.

FIG. 14 illustrates an exemplary registration message and the contentsof the registration message in accordance with an exemplary embodimentof the invention.

SUMMARY OF THE INVENTION

Methods and apparatus of the present invention can be used to supportsession signaling and mobility management in a network including aplurality of end nodes that interact via one or more access nodes aredescribed. The access nodes may be implemented as wireless accessrouters which include receiver and transmitter circuitry and aninterface to support communications with end nodes, e.g., mobile nodes,via a wireless communications channel. The access nodes may be, forexample, base stations in a cellular communications system. Theinterface in each access node may also include circuitry for couplingthe access node to another node, e.g., an intermediate node used tocouple two or more access nodes together.

A network implemented in accordance with the present invention includesone or more access nodes of the present invention through which endnodes can establish and conduct communications sessions. End nodes maybe, for example, mobile devices which include or are IP hosts. An accessnode implemented in accordance with some embodiments of the presentinvention includes, a session signaling module in addition to a mobilityagent module. In some but not all embodiments, the sessions signalingmodule is included in the same access node housing as the mobility agentmodule. Access nodes need not include a session signaling module in allcases. An authentication module, network resource information and stateinformation are also included in the access node in some embodiments.The session signaling module may be, e.g., a Session Initiation Protocol(SIP) server while the mobility agent module may be implemented as aMobile IP module. The various modules comprising an access node inaccordance with the invention are implemented in a fashion that allowsresource and state information from each module as well as the otherparts of the access node to be visible, used and/or updated by oneanother.

Various features of the present invention facilitate session signalingaddress registration operations and are intended to reduce the number ofsession signaling registration messages that need to be transmitted asan end node registers while in a foreign domain, with home sessionsignaling servers in one or more home domains associated with the endnode. For purposes of explanation the end node will sometimes be calleda mobile node. However, it is to be understood that the end node couldalso be a fixed node.

In accordance with one feature of the present invention, the homesession signaling server stores information associating a sessionsignaling address of an access node in the visited domain with a sessionsignaling address of an end node, e.g., a mobile node, while the mobilenode is using said access node in the visited domain as a point ofnetwork attachment. The home session signaling server routes sessionsignaling packets addressed to the mobile node using the stored addressinformation to the address of the access node in the visited domain. Theaccess node then routes the received packets intended for the visitingmobile node to the mobile node, e.g., via a wireless link.

In some embodiments, the access node in the visited domain detectssession signaling messages directed to a home session signaling server,intercepts said messages, and then transmits session signaling messagesto the home session signaling server which include the session signalingaddress of the access node. The generation of the registration messagetransmitted from the access node to the home session signaling servermay involve an address translation operation which involves replacing atleast a portion of the mobile node's session signaling address, includedin the intercepted registration message, with at least a portion of theaccess node's session signaling address.

In order to reduce the amount of communications resources used totransmit session signaling registration messages from mobile nodes toaccess nodes, in accordance with one feature of the present invention,broadcasting of session signaling messages is supported by access nodes.In one broadcast embodiment, when a session signaling registrationmessage is received by an access node, the access node checks storedinformation to determine if multiple home session signaling servers areto be supplied with a session signaling message. In such an embodiment,a list of home session signaling server addresses is maintained andassociated with mobile node addresses in the access node. The accessnode compares a mobile node session signaling address included in thereceived registration message to determine if the message should betransmitted to multiple home session signaling servers listed in thestored information, e.g., in associated with the mobile node's address.In response to determining that a received registration message is to bebroadcast, the access node transmits the message, or a modified versionof the received session signaling registration message, to the homesession signaling servers indicated in the set of stored information.

In accordance with another session signaling registration messagebroadcast feature, a novel session signaling registration message issupported. The novel session signaling registration message includesmultiple end node session signaling identifiers, e.g., addresses ofdifferent home session signaling servers. The multiple end node sessionsignaling identifiers are in addition to a target field and a contactfield. The novel registration message is transmitted from a mobile nodeto an access node. The access node receives and processes theregistration message. In response to the registration message, theaccess node transmits a separate session signaling registration messageto at least two, e.g., each, of the home session signaling serversidentified by the multiple end node session signaling identifiersincluded in the received registration message. As part of theregistration message signaling process, the novel session signalingregistration message is stored in a machine-readable medium, e.g., abuffer, memory, or other storage device, included in the end nodetransmitting the message and also in the access node receiving themessage.

Through the use of the above-described broadcast techniques, the amountof bandwidth used to transmit session signaling registration messagescan be reduced as compared to systems which do not use such broadcasttechniques.

In order to reduce the number of session signaling address registrationmessages transmitted between network domains, e.g., a visited domain andone or more home domains, in various embodiments a paging and locationserver is used in the visited domain. When in the visited domain, avisiting end node registers its session signaling address with thepaging and location server in the visited domain. It also registers thesession signaling address of the paging and location server in thevisited domain with its home session signaling servers. The home sessionsignaling server directs packets to the end node in the visiting domainto the paging and location server which then directs them to the accessnode in the visiting domain to which the visiting end node is coupled toat any given point in time. As the visiting end node moves from accessnode to access node in the visited domain, it updates its sessionsignaling address information that has been stored at the paging andlocation server. However, it does not have to update the sessionsignaling address information stored at its home session signalingserver since that information remains valid since the paging andlocation server used by the visiting node remains unchanged. In thismanner, the need to transmit session signaling registration messages toone or more home session signaling servers after a handoff in a visiteddomain is reduced or avoided.

The modules included in the access nodes, paging and location server andhome session signaling servers of the invention are implemented usingsoftware, hardware or a combination of software and hardware. In thecase of software implementations, the modules include differentinstructions or sets of instructions used to control hardware, e.g.,circuitry, to implement each of the different operations performed bythe module.

Numerous additional embodiments, features, and advantages of the methodsand apparatus of the present invention are discussed in the detaileddescription that follows.

DETAILED DESCRIPTION

FIG. 2 illustrates an exemplary access node 200 implemented inaccordance with the present invention. In the FIG. 2 embodiment, theaccess node 200 includes an input/output interface 201, a processor 203and memory 212, coupled together by bus 205. The elements 201, 203, 212,205 of access node 200 are located inside a housing 211, e.g., a case ofplastic and/or metal, represented by the rectangle surrounding thenode's internal elements 201, 203, 212, 205. Accordingly, via bus 205the various components of the access node 200 can exchange information,signals and data. The input/output interface 201 provides a mechanism bywhich the internal components of the access node 200 can send andreceive signals to/from external devices and network nodes. Theinput/output interface 201 includes, e.g., a receiver circuit andtransmitter circuit used for coupling the node 200 to other networknodes, e.g., via fiber optic lines, and to end nodes, e.g., via wirelesscommunications channels.

The processor 203 under control of various modules, e.g., routines,included in memory 212 controls operation of the access node 200 toperform various signaling, session admission, resource allocation,authentication, and other operations as will be discussed below. Themodules included in memory 212 are executed on startup or as called byother modules. Modules may exchange data, information, and signals whenexecuted. Modules may also share data and information when executed. Inthe FIG. 2 embodiment, the memory 212 of access node 200 of the presentinvention includes a mobility agent module 202, a session signalingserver module 204 and an authentication module 208 as well as resourceinformation 206 and state information 210.

Resource information 206 includes, e.g., parameters, resource limitsboth internal to the access node 200 as well as on its interfaces 201,indication and/or accounting of active sessions and/or used resourcesand/or available resources both internal to the access node 200 as wellas on its interfaces 201. State information 210 includes, e.g.,parameters, communication session and/or end node status information,security information, and/or other information relating to end nodeinteraction and/or communication with an access node and/or anotherdevice.

The session signaling server module 204 allows the access node 200 tosupport session initiation operations, e.g., processing of receivedsignals or messages used for the establishment of a data communicationsessions and sending of subsequent signals or messaging as required. Thesession signaling server module 204 also supports session maintenanceand termination services. During a session initiation operation as partof an admission control step the session signaling server may take intoaccount and keep track of available resources. Thus, the sessionsignaling server may access and update the resource information 206,which is kept in memory 212, e.g., information on available remainingbandwidth not allocated to active sessions.

The mobility agent module 202 allows the access node 200 to support endnode mobility and connectivity management services. Thus, the accessnode 200 is capable of providing node mobility, session establishment,and session maintenance services to connected end nodes. The mobilityagent module 202 may be implemented in a plurality of ways. In the FIG.2 embodiment it is implemented with a collection of sub-modules. Asillustrated, the mobility agent module 202 includes sub-modules 242,244, 246, which operate as a Mobile IPv4 Foreign Agent, a Mobile IPv6Attendant, and a Host Routing Agent, respectively. By includingsub-modules 242, 244 the mobility agent module 202 is capable ofsupporting multiple versions of Mobile IP signaling including MobileIPv4 and Mobile IPv6 signaling. In various embodiments, the mobilityagent module 202 includes a subset of the sub-modules 242, 244 and 246shown in FIG. 2. For example, in embodiments where Mobile IPv6 is notrequired, the mobile IPv6 Attendant sub-module 244 may be omitted.

As shown in FIG. 2, the exemplary mobility agent module 202 includes acontext transfer sub-module 248 used to perform information, e.g.,state, transfer operations as part of a handoff. As part of a handoffoperation executed by the mobility agent module 202 when an end nodechanges its point of connection from the access node 200 to anotheraccess node, or vice versa, the context transfer sub-module 248 performsan operation to support the transfer of state information 210 regardingthe end node from one access node to the next. The state information 210that is transferred includes state information provided by other modulesin memory 212. In particular, the state information 210 includes datacommunication session state and session establishment state provided bythe session signaling server module 204, as well as authentication stateand other security related state provided by the authentication module208. In the present context “state” is used to broadly refer toinformation about a state, e.g., of a device, node, or communicationssession. In alternative embodiments of the invention the mobility agentmodule 202 may also include additional sub-modules to support a numberof mobility related functions that improve the performance of handoffand minimize service disruption. In another alternative embodimentequivalent context transfer functionality may be implemented as aseparate module in memory 212, as opposed to a sub-module of themobility agent module 202.

The authentication module 208 included in memory 212 of the access node200 is capable of authenticating messages and signals from other networknodes and end nodes connecting to the access node 200 via theinput/output interface 201. The authentication module 208 also providesauthentication services to other modules and sub-modules included in thememory 212 of the access node 200. Thus, the authentication module 208can check the validity of messages and signals received by other modulesand sub-modules in memory 212, e.g., the session signaling server module204. Authentication module functionality can be incorporated directlyinto other modules or sub-modules instead as a separate module 208.

Incorporating a session signaling server module 204, mobility agentmodule 202, and authentication module 208 inside the housing 211 of anaccess node 200 where resource information 206 and state information 210can be easily accessed, provides significant advantages in terms ofsignaling complexity associated with session establishment andmaintenance over the FIG. 1 system.

While shown as software module in the FIG. 2 implementation, each of themodules 204, 202, 208, and sub-modules included therein, can beimplemented using hardware, software or a combination of software andhardware. For purposes of the invention described herein, references tomodules or sub-modules are to be understood as software, hardware or acombination of software and hardware that performs the functions of thedescribed module or sub-module.

In accordance with one particular embodiment of the present invention,the session signaling server module 204 is a SIP (Session InitiationProtocol) server. In a particular embodiment, the access node 200 isimplemented as a wireless access router that supports forwarding of IP(Internet Protocol) datagrams. In such an implementation input/outputinterface 201 includes circuitry, e.g., receiver/transmitter circuitry,that allows end nodes to connect to the access node 200 using wirelesscommunications technology, e.g., via wireless communications channels.In one such implementation the coverage area of the access node iscalled a communication “cell”. In alternative embodiments, the sessionsignaling server module 204 sends, receives and processes signal basedon other protocols such as the Resource Reservation Protocol (RSVP). Insome embodiments the session signaling server module 204 supports bothSIP and RSVP signaling. In some embodiments the input/output interface201 includes circuitry that allows end nodes to connect to it via wired,wireless or a combination of wired and wireless communicationstechnologies.

FIG. 3 illustrates an exemplary system 400 that comprises a plurality ofaccess nodes 200, 200′, 200″ implemented in accordance with the presentinvention. FIG. 3 also depicts communication cells 300, 300′, 300″surrounding each access node 200, 200′, 200″, respectively, whichrepresents the coverage area of corresponding access node 200, 200′,200″, respectively. The same physical and functional elements aredepicted in each of the communication cells, thus the followingdescription of the elements in the cell 300 surrounding access node 200is directly applicable to each of the cells 300, 300′, 300″. Thedepiction of the access node 200 is a simplified representation of theaccess node 200 depicted in FIG. 2. The illustration of the access node200 in FIG. 3 depicts the mobility agent module 202, session signalingserver module 204, authentication module 208, resource information 206and state information 210, while some other elements are not shown. Aset of arrows 207 is used to represent the exchange of data,information, and signals between the depicted elements when they areexecuted. While the input/output interface 201 is not shown in FIG. 3,connectivity between access node 200 and other network nodes is shownand is subsequently further described. FIG. 3 illustrates the accessnode 200 providing connectivity to a plurality of N end nodes 302, 304via corresponding access links 306, 308.

Interconnectivity between the access nodes 200, 200′, 200″ is providedthrough network links 310, 311, 313 and an intermediate network node320. The intermediate network node 320 also provides interconnectivityto another network 330 via network link 322, where the network 330 isthe home network of end node X 304. The home network 330 includes a homemobility agent node 332 and a home session signaling server node 334,each of which is connected to an intermediate network node 336 by one oftwo network links 338, 340, respectively. The intermediate network node336 in the home network 330 also provides interconnectivity to networknodes that are external from the perspective of the home network 330 vianetwork link 322.

The home mobility agent node 332 in the system 400 allows end node X 304to maintain reachability as it moves between access nodes 200, 200′,200″. The home mobility agent node 332 is responsible for redirectingpackets to the current location of end node X 304 by maintaining amapping between the home address and an address associated with theaccess node through which end node X 304 is current connected. The homesession signaling server 334 in the system 400 provides sessionsignaling and redirection services to facilitate establishment of datacommunication sessions to end node X 304.

Alternative embodiments of the invention include various networktopologies, where the number and type of network nodes, the number andtype of links, and the interconnectivity between nodes differs from thatof the system 400 depicted in FIGS. 3 to 6.

FIG. 4 illustrates the signaling performed in the exemplary system 400shown in FIG. 3 as part of the processes of initiating and conducting adata communication session between a first mobile end node X 304 andsecond end node Y 304″ in accordance with an exemplary embodiment of theinvention. The following description of how end nodes 302, 304 obtainservice through access node 200, including the methods forauthentication and discovery of an identifier, e.g., address, isrepresentative of similar operations that may be performed by end nodes(302, 304), (302′, 304′), (302″, 304″) and the corresponding access node200, 200′, 200″, respectively. In order to obtain service through theaccess node 200, end nodes 302, 304 perform various signaling and otheroperations when they enter the coverage area of an access node 200. Thespecific details of these signals and operations vary depending on theunderlying communication technology and protocols used. In the FIG. 4embodiment of this invention, an authentication module 208 in an accessnode 200 uses an end node specific secret value to authenticate signals,e.g., messages, received from an end node 302, 304 during an initialaccess phase and uses the same secret value to validate messagessubsequently received by other modules, e.g., the session signalingserver module 204. In addition to using the same secret value, theauthentication module 208 may also use the same method to perform theauthentication operation for messages received by the various modules.

In the FIG. 4 embodiment of this invention, the mobility agent module202 and session signaling server module 204, each of which is includedin the access node 200, can be contacted using the same identifier. Theidentifier may be, e.g., an IP address associated with both modules 202,204. According to this invention the shared identifier, e.g., address,is made known to the end nodes 302, 304 within the coverage area ofaccess node 200 by sending a signal, e.g., message 402 from the accessnode 200 to the end nodes 302, 304. Similarly, end nodes in theexemplary system 400 receive this identifier, e.g., address, informationfrom their corresponding access node through which they access thecommunications system 400. In one particular embodiment of thisinvention an access node 200 periodically broadcasts a signal, e.g.,message 402, including the identifier, e.g., address, information. Inalternative embodiments an end node 302, 304 solicits the identifier,e.g., address, information by sending a signal, e.g., message, when itenters the coverage area of an access node 200. The access node 200 thenresponds by sending a signal, e.g., message, including the requestedidentifier, e.g., address, information to the end node. An access node200 may also use a combination of the two methods, in which case accessnode 200 periodically broadcasts a signal, e.g., message, including theidentifier, e.g., address, information and also responds to specificsolicitations from end nodes 302, 304.

In the FIG. 4 illustration, end node Y 304″ initiates establishment of adata communication session with end node X 304. End node Y 304″ firstsends a request session signaling message 404 to end node X 304 via thesession signaling module 204″ in the access node 200″. While the requestmessage 404 is directed to the session signaling module 204″, therequest message 404 also identifies end node X 304 as the target ofsession establishment request. The session signaling module 204″ inaccess node 200″ receives the request message 404, adds its ownidentifier, e.g., address, to the request message and redirects therequest message 406 to the home session signaling server 334 of the endnode X 304. The home session signaling server 334 receives the requestmessage 406, adds its own identifier, e.g., address, to the requestmessage and redirects the request message 408 to the currentlyregistered location of end node X 304, which is the session signalingmodule 204 in access node 200 to which end node X 304 is connected.

Following reception of the request message 408 from the home sessionsignaling server 334, the session signaling module 204 in access node200 accesses state information 210 associated with the mobility agent202 to control redirection of the request message. Since the stateinformation 210 indicates that end node X 304 is directly connected viaaccess link 308, the session signaling server module 204 does not haveto direct the request message to the home mobility agent 332 of end nodeX 304. Instead it adds its own identifier, e.g., address, to the requestmessage 408 and delivers the request message 410 directly to end node X304 over access link 308.

Following reception of the request session signaling message 410, endnode X 304 sends a response session signaling message 412 back to endnode Y 304″. The response message 412 from end node X 304 to end node Y304″ takes the reverse path specified by the list of identifiers, e.g.,addresses, of intermediate session signaling nodes included in thereceived request message. In particular, the response message 412 issent from end node X 304 to the session signaling module 204. Sessionsignaling server module 204 sends the response message 414 to homesession signaling server node 334, which sends the response message 416to session signaling server module 204″ in access node 200″. The sessionsignaling server module 204″ in access node 200″ then sends the message418 to end node Y 304″, which completes the session signalingtransaction.

According to this invention since the session signaling server modules204, 204″ in the access nodes 200, 200″, respectively, are in thesession signaling path, they have access to the information in thesession signaling message that describe the session's resourcerequirements. Resources such as a minimum bandwidth on the access linkmay be required for sessions to operate appropriately. Additionally, thesession signaling modules 204, 204″ have access to the current accessnode load levels and local policy contained in resource information 206,206″ and state information 210, 210″. Based on this information thesession signaling servers 204, 204″ in the access nodes 200, 200″ canadmit or reject the session that end node X and end node Y attempt toestablish. If a session is admitted, the session signaling servermodules 204, 204″ reserve these resources in the access nodes 200, 200″.

In the exemplary embodiment of this invention end node X 304 is mobileand thus can at any time move between the communication cells 300, 300′,300″. FIGS. 5 and 6 illustrate signaling performed in the exemplarysystem 400 shown in FIG. 3 as part of the processes of initiating andconducting a data communication session between a, first mobile end nodeX 304 and second end node Y 304″ in accordance with an exemplaryembodiment of the invention, while the target end node X 304 is in theprocess of handing off between a first access node 200 and a secondaccess node 200′. The movement of end node X 304 in FIGS. 5 and 6 isdepicted with a double arrow 426, 430 in each figure, respectively. Forillustration purposes FIGS. 5 and 6 depict the signaling and interactionbetween nodes according to an exemplary timing of events describedbelow. Similar but not necessarily identical processes will apply if thetiming of the events is modified.

As shown in FIG. 5, end node Y 304″ first sends a request sessionsignaling message 420 to end node X 304 via the session signaling module204″ in the access node 200″. While the request message 420 is directedto the session signaling module 204″, the request message 420 alsoidentifies end node X 304 as the target of session establishmentrequest. The session signaling module 204″ in access node 200″ receivesthe request message 420, adds its own identifier, e.g., address, to therequest message and redirects the request message 422 to the homesession signaling server 334 of the end node X 304. The home sessionsignaling server 334 receives the request message 422, adds its ownidentifier, e.g., address, to the request message and redirects therequest message 424 to the currently registered location of end node X304, which is the session signaling module 204 in access node 200 towhich end node X 304 is connected.

Prior to the arrival of request message 424 at the session signalingserver module 204, end node X 304 changes its point attachment to thenetwork from a first access node 200 to a second access node 200′. Notethat FIG. 5 shows end node X 304 connected to the first access node 200via access link 308, while FIG. 6 shows end node X 304 connected to thesecond access node 200′ via access link 305. FIG. 6 illustrates ahandoff operation 432 that is coordinated by the mobility agent modules202, 202′ in access nodes 200 and 200′. As part of the handoff operation432, state information 210 associated with end node X 304 is transferredfrom the first access node 200 to the second 200′. Transferredinformation includes, for example, authentication information, sharedsecrets, and unique identifiers for previously admitted sessions as wellas any associated session state for end node X 304 in access node 200.During and for a predetermined period of time following the handoffoperation 432, the mobility agent module 202 in the first access node200 maintains state information 210 regarding the new point ofattachment of end node X 304, e.g., an identifier or address of thesecond access node 200′. Thus, upon arrival of request message 424 fromthe home session signaling server 334, the session signaling module 204in access node 200, accesses the state information 210 associated withthe mobility agent 202 to control redirection of the request message.Since the state information 210 in the first access node 200 indicatesthat end node X 304 has changed its point of attachment to the secondaccess node 200′, the session signaling server module 204 in the firstaccess node 200 optionally add its own identifier, e.g., address, to therequest message and immediately redirects the request message 434 to thesession signaling server module 204′ in the second access node 200′, asshown in FIG. 6. Note that in the exemplary embodiment, the sessionsignaling server module 204 in the first access node 200 does not addits own identifier, e.g., address, to the request message 434 that isdirected to the session signaling server module 204′ in the secondaccess node 200′.

Following reception of the request message 434 from the sessionsignaling server module 204 in the first access node 200, the sessionsignaling module 204′ in the second access node 200′ accesses stateinformation 210′ associated with the mobility agent 202′ to controlredirection of the request message. Since the state information 210′indicates that end node X 304 is directly connected via access link 305,the session signaling server module 204′ does not have to direct therequest message to the home mobility agent 332 of end node X 304.Instead, it adds its own identifier, e.g., address, to the requestmessage 434 and then delivers the request message 436 directly to endnode X 304 over access link 305.

Following reception of the request session signaling message 436, endnode X 304 sends a response session signaling message 438 back to endnode Y 304″, as shown in FIG. 6. The response message 438 from end nodeX 304 to end node Y 304″ takes the reverse path specified by the list ofidentifiers, e.g., addresses, of intermediate session signaling nodesincluded in the received request message. In particular, the responsemessage 438 is sent from end node X 304 to the session signaling module204′. Session signaling server module 204′ sends the response message440 to home session signaling server node 334, which sends the message442 to session signaling server module 204″ in access node 200″. Thesession signaling server module 204″ in access node 200″ then sends themessage 444 to end node Y 304″, which completes the session signalingtransaction. Recall that in the exemplary embodiment, the sessionsignaling server module 204 in the first access node 200 did not add itsown identifier, e.g., address, to the request message 434 that wasdirected to the session signaling server module 204′ in the secondaccess node 200′ and therefore is not included in the reverse path.

While session signaling between end node Y 304″ and end node X 304 isdescribed to go via the session signaling server modules 204″ and 204 inaccess nodes 200″ and 200 and only one additional session signalingserver node 334 in the network, in several embodiments of this inventionthe request/response messages may go through a number of other sessionsignaling nodes in the network according to network policy and messagerouting.

While in the description above the session signaling server modules 204,204″ reserve the resources required directly in an alternativeembodiment of this invention, end nodes 304, 304″ and/or sessionsignaling servers 204, 204″ may use resource reservation protocolmessages, such as RSVP messages, to reserve the resources for anadmitted session. In one embodiment of the invention and during theadmission phase for a given session the access node 200 generates aunique identifier and associates it with the admitted session. Thisidentifier is unique in this access node 200 and also in any otheraccess nodes 200′ 200″ to which the end node X 304 may move to duringthe lifetime of the session. In one particular embodiment the accessnode 200 ensures uniqueness of the identifier by combining a valueassociated with end node X 304 and another value associated with accessnode 200. Similarly a unique identifier is generated by access node 200″for the same session to which end node Y 304″ participates.

While session request signals from the end nodes, such as signal 404 inFIG. 4 are shown as being explicitly sent directly to the sessionsignaling server module, e.g.: 204″ in FIG. 4, in another alternativeembodiment of this invention the request session signaling message 404from end node Y 200″ is not directed to the session signaling module204″ in the immediate access node 200″, but is instead sent to anothersession signaling node in the network, e.g., the home session signalingserver 334 of end node X 304. In such a case the session signalingmodule 204″ in access node 200″ would intercept, e.g., snoop, themessage 404 and inspect the message 404 to extract the informationrequired so that the session can be admitted or rejected. In such animplementation, we refer to the session signaling server module 204″ asa snooping session signaling module. In an alternative embodiment ofthis invention the snooping session signaling module also adds itsidentifier, e.g., address, to the message before it send the message tothe next session signaling node. Responding messages will thusexplicitly go through the snooping session signaling module. The sameprocedure is repeated at the receiving end when the request sessionsignaling message is not directed to the session signaling module 204 inaccess node 200. The session signaling module 204 instead intercepts thesession signaling message 408, extracts the information needed forsession admission and optionally adds its own identifier, e.g., address,to the message so that response session signaling messages will gothrough it in an explicit manner.

Additional aspects, features, methods, apparatus and exemplaryembodiments which are part of the inventive methods and apparatus towhich the present patent application is directed are described in thefollowing U.S. Provisional patent applications each of which is herebyexpressly incorporated by reference into the present patent application.

-   -   1. U.S. Provisional Patent Application Ser. No. 60/298,283,        filed on Jun. 14, 2001, titled: “Location of SIP Proxy Server in        Wireless Access Router”.    -   2. U.S. Provisional Patent Application Ser. No. 60/369,016,        filed on Apr. 1, 2002, titled: “Methods and Apparatus for        Registration for SIP Services in Mobile Networks”.    -   3. U.S. Provisional Patent Application Ser. No. 60/370,524,        filed on Apr. 5, 2002, titled: “Methods and Apparatus for SIP        Message Forwarding and Redirection”.    -   4. U.S. Provisional Patent Application Ser. No. 60/313,035,        filed on Aug. 16, 2001, titled: “A Method for Controlling IP        Applications During Network Changes that Result in Resource        Shortages”.

As a result of the above incorporation by reference, the text andfigures of the listed provisional patent applications form part of thepresent description. It is to be understood that the reference numeralsused in the text and figures of the provisional patent applications areto be interpreted in the context of the particular incorporatedprovisional application and are not to be interpreted as the same as anysimilarly numbered element or elements described in the above text orthe figures which are included herein without the use of anincorporation by reference. It is to be further understood thatmandatory language in the incorporated provisional applications such as“vmust”, “only”, etc., if any, is to be interpreted as being limited tothe exemplary embodiments described in the provisional applications andis not to be interpreted as a limitation on the embodiments, figures,and claims of the present application which are not incorporated byreference.

In the descriptions below we differentiate between the network addressof a node and the session signaling address of the same node or itsuser. A network address is the address used to send a data packet viathe routing network infrastructure to the owner node of that address. Asession signaling address is used to send a signaling message todestination which typically involves the resolution of the sessionsignaling address to a network address and the transmission of packet orpackets to that network address. A Session signaling address typicallyhas a “user” part and a “domain” part. The Network Access Identifier(NAI) and the Session Signaling Protocol Universal Resource Identifier(SIP-URI) are some examples of such an address. The typical format ofsaid address is user@domain. The “domain” part identifies the operator'snetwork or domain the user belongs to e.g.: Flarion.com. The domain partcan typically be resolved to an actual network address such as anInternet Protocol (IP) Address via a database system e.g.: the DomainName System (DNS). The “user” part identifies the user in the saiddomain e.g.: JohnSmith. The resultant address is JohnSmith@Flarion.com.To initiate session signaling communications with JohnSmith@Flarion.comone needs to send a session signaling message to JohnSmith@Flarion.com.This is achieved by resolving the domain part “Flarion.com” to thenetwork address of the session signaling server for said domain andsending the message to that server. The Session Signaling Server thenforwards the message to the current location of JohnSmith. If JohnSmithis in the same domain then his forwarding address may be something likeJohnSmith@10.0.0.1 where 10.0.0.1 is an example of a network addressthat JohnSmith may be currently located. If JohnSmith is currently at adifferent domain e.g.: foreign.com then his forwarding address maybecome a concatenation of his session signaling address and the domainaddress of the visiting domain. E.g.: JohnSmith%Flarion.com@foreign.com.

An Operator's Domain or Network is a set of communication equipment(including routers, switches, cables, servers and other) under theownership and administration of an Operator. An Operator may havemultiple domains but a single domain is owned by a single operator.

FIG. 7 illustrates a multi-domain network diagram of a communicationssystem 1000 implemented in accordance with an exemplary embodiment ofthe invention. Various messaging features of the system 1000 will bedescribed in detail with reference to FIGS. 9 and 10 that show signalingperformed in the system 1000 in accordance with various exemplaryembodiments of the invention. The system 1000 is similar to theexemplary system 400 of FIG. 3 and may be implemented using many of theelements previously described with regard to FIG. 3. Like numberedelements in FIGS. 3 and 7 may be implemented using the same or similarelements. For the purposes of brevity, such elements will not bedescribed in detail again.

Differences between FIG. 3 and FIG. 7 will now be described. Cell 300″of FIG. 3 is replaced by a second home network 330′ in FIG. 7. Thesecond home network 330′ is connected to the rest of the network vianode 320 which is coupled to the second home network 330′ by link 1111.Exemplary system 1000 spans three different domains: a home domain 13001, a home domain 2 3002, and a visited domain 3003. Home domain 13001 is separated from home domain 2 3002 by line 1220. Home domain 13001 and home domain 2 3002 are both separated from the visited domain3003 by line 1210. Home network 330 is located in home domain 1 3001.Home network 330′ is located in home domain 2 3002, while the rest ofthe exemplary system 1000 is shown to be located in the visited domain3003. Home session signaling servers 1200 and 1200′, of home networks330 and 330′ respectively, of FIG. 7 are similar to and replace the homesession signaling server 334 of home network 330 in FIG. 3. States 1201,1201′ incorporated in home session signaling servers 1200 and 1200′ ofFIG. 7 are emphasized in the figure since the states 1201,1201′ are tobe manipulated, e.g., modified and updated, in accordance with variousfeatures of the present invention. States 1201, 1201′ are sets of storedinformation which include information on various mobile nodes and thecommunication state of each mobile node. The state information 1201,1201′ includes information used for routing IP packets and for signalingpurposes as will be discussed further below. Access nodes 1100, 1100′located within cells 300 and 300′ within the visited domain 3003 of FIG.7 may be implemented using the same or similar hardware as used toimplement access nodes 200, 200′ as shown in FIG. 3, but the operationof access nodes 1100 and 1100′ has been extended by the addition ofcontrol routines and/or modules used to control the access node tooperate in accordance with the methods described below with reference toFIGS. 9 and 10. Session signaling server modules 1110, 1110′ of accessnodes 1100, 1100′ respectively of FIG. 7 are similar to sessionsignaling server modules 200 and 200′ shown in FIG. 3. State information1120, 1120′ of access nodes 1100, 1100′ respectively, of FIG. 7 aresimilar to state information 210 and 210′ as shown in FIG. 3. End nodes1001, 1002, of cell 300 and end nodes 1001′, 1002′ of cell 300′ shown inFIG. 7 are also identical or similar with corresponding end nodes 302,304 and 302′, 304′ respectively as shown in FIG. 3. Session signalingserver modules 1110, 1110′, state information 1110, 1110′, and end nodes1001, 1002, 1001′, 1002′ have been equipped, e.g., include routines,which cause one or more of these elements to operate in the mannerdescribed below with regard to FIGS. 9-10.

FIG. 8 illustrates an exemplary system 2002 that is similar to theexemplary system 1000 of FIG. 7 but which has been enhanced by theaddition of a Paging and Location Server (PLS) 1300 in accordance withon embodiment of the invention. The PLS 1300, in accordance with thepresent invention servers as a repository of location registrationinformation for a mobile node in a visited domain. As such, it can serveas an intermediary which can send messages used to update the stateinformation in the visiting node's home session signaling server. Oncethe home session signal server 1200 is made aware of the PLS 1300 beingused by a mobile node in a visited domain, it can contact the mobilethrough the PLS 1300 in the visited domain. As will be discussed furtherbelow, as the mobile moves from one access node to another access nodewhile remaining in the visited domain, the PLS server 1300 in thevisited domain is updated to reflect the change in location but thelocation information in the home session signaling server need not beupdated since the PLS 1300 servicing the mobile node in the visiteddomain remains unchanged.

Like numbered elements in FIGS. 7 and 8 may be implemented using thesame or similar elements. Since the like numbered elements have alreadybeen described in detail with regard to FIG. 7 and/or one of thepreceding figures, for purposes of brevity, those elements will not bedescribed in detail again. The differences between FIG. 7 and FIG. 8 aredescribed below. The second home network 330′ of FIG. 7 connected to therest of the network via link 1111 has been removed in the exemplarysystem 2002 to simplify the figure but may be used in actualimplementations. Exemplary system 2002 also spans two different domains,home domain 1 3001 and the visited domain 3003, which are separated byline 1210. Home network 330 is located in the home domain 1 3001, whilethe rest of the exemplary system 2002 is shown to be located in avisited domain 3003. Paging and location server (PLS) 1300 includes aprocessor, input/output interface and memory. The memory includesroutines which control the PLS 1300 to store state information 1301 inits memory and receive and transmit messages including registrationmessages, in accordance with the present invention. The PLS 1300 islocated in the visited domain 3003 and is connected to the network vianode 320 which is connected to the PLS by link 1302. As will bediscussed below with regard to FIGS. 12 and 13, PLS 1300 performs,depending on the embodiment, a wide variety of operations associatedwith communicating mobile node location information to one or moresession signaling servers include, e.g., a visiting mobile node's homesession signaling server 1200 located in the home domain 3001.

The network topology shown in FIGS. 7 and 8 are exemplary and intendedfor purposes of explaining the invention. The methods and apparatus ofthe present invention include can be used with a wide range of networktopologies, where the number of domains, the number and type of networknodes, the number and type of links, the number and type of cells, thenumber and type servers, the interconnectivity between nodes, and theinterconnectivity between servers and nodes, differs from that of theexemplary systems 1000, 2002 depicted in FIGS. 7 and 8.

For the purpose of illustration we give exemplary network and sessionsignaling addresses in the different elements used in FIGS. 7 to 13.

Session Signaling Addresses

-   Home Session Signaling Server 1200: Home1.com-   Home Session Signaling Server 1200′: Home2.com-   Paging and Location Server 1300: PLS.com    Network Addresses-   Access Node 1100: 20.0.0.1-   Access Node 1100′:20.0.1.1-   End Node X 1002: 10.0.0.1

FIG. 9 illustrates a simplified version of the exemplary system 1000 ofFIG. 7 and depicts session signaling performed as part of the processesof registering the forwarding address of end node X 1002 to its homesession signaling server 1200 via access node 1100 in accordance withone embodiment of the present invention.

In accordance with a first signaling method of the present invention,the mobile node, e.g., end node X 1002 is not aware of the presence ofsession signaling server module 110 in the access node 1100 throughwhich it connects to is home domain 3001. The signaling associated withsuch an embodiment is shown in FIG. 9.

In the FIG. 9 embodiment, in order to register its location with itsHome session signaling server 1200, end node X 1002 sends a REGISTERmessage 1400 directed to the network address of the home sessionsignaling server node 1200. Since the access node serves as the mobilenode's point of network attachment, this message is routed throughaccess node 1100 where it is processed.

In accordance with the present invention, Session Signal Server module1110 monitors for message to home session signaling server 1200 and, inresponse to detecting such a message intercepts and processes themessage. In particular the Session Signaling Server module 1110processes the received message to generate one or more new Registermessages there from. The module 1110 also stores relevant addressinformation in its set of State information 1120. In accordance with theembodiment shown in FIG. 9, the session signaling server module 1110generates and transmits a new register message 1410 to the mobile node'shome session signaling server 1200. As will be discussed further below,the processing performed by the session signaling server module mayinclude message modification operations including address translationoperations associated with generating the message 1410. It may alsoinvolve a broadcast operation as will be discussed with reference toFIG. 10.

The REGISTER message 1400 includes three main fields, a target field, arecord field, and a contact field. The target field includes the addressof the device to which the REGISTER message is directed, e.g., theaddress of home session signaling server node 1200. The record part ofthe message 1400 includes the home session signaling address of theregister message source, e.g., End Node X. The contact field of theRegister message 1400 includes the forwarding address to be used forrouting message to End Node X when outside the home domain 3001 in whichthe end node's home session signaling server 1200 is located.

In one embodiment, the session signaling server module 1110 modifies thereceived message 1400 by performing a translation operation to thecontact field of the received message 1400 changing its value to a valuethat includes the access node's 1100 network address. In one particularembodiment, the contact field is translated to become a sessionsignaling address that is the result of amending the access node's 1100network address to the session signaling address of end node X 1002.

The first row of Table 1, set forth below, illustrates the exemplarycontents of the three fields of an exemplary Register message 1400. Thefirst row of table 1 correspond to message 1400 which is transmittedfrom a Mobile Node, e.g., exemplary mobile node X in the case of theFIG. 14 example, addressed to the mobile nodes Home Session SignalingServer. 1200. While the first column identifies the message listed inthe particular row of Table 1, the second, third and fourth columns ofeach row are used to show exemplary contents of the messages Target,Record and Contact fields, respectively. The target field correspondingto message 1400 shown in Table 1, includes the session signaling addressof End node X's home session signaling server node 1200. The homesession signaling address of end node x 1002 is included in themessage's record field. Meanwhile, the end node X's own network addressis part of the node's session signaling address which is included in thecontact field of exemplary message 1400.

The second row of Table 1 shows the three fields of an exemplaryRegister message 1410, generated by processing the register messageshown in the first row.

TABLE 1 REGISTER MESSAGE CONTENT MESSAGE Target Record Contact MessageHome Session Home Session Forwarding Session 1400 Signaling ServerSignaling Address of Signaling Address of ENx from Address End Node X(ENx) with domain part equal to Mobile network address of ENx Node (MN)User= NULL User= user of ENx User= user of ENx (e.g. End Domain= domainof Domain= domain of Domain= Network Address of Node X HSSSN HSSSN ENx(ENx)) Example: Example: Example: addressed Home1.com ENx@Home1.comENx@10.0.0.1 to Home Session Signaling Server Node (HSSSN) Access NodeHome Session Home Session Forwarding Session (AN) Signaling ServerSignaling Address of Signaling Address of ENx Intercepts, Address ENxModifies User= NULL User= user of ENx User= Home Session ContactSignaling address of ENx field and (User=user of ENx, forwardsDomain=domain of HSSSN) message Domain= domain of Domain= domain ofDomain= Network Address of 1410 HSSSN HSSSN access node 1100 addressedExample: Example: Example: to HSSSN Home1.com Home1.comENx%Home1.com@20.0.0.1

Access node 1100 add and maintains the session signaling address of theend node X 1002 obtained from the received Register message 1400 instate information 1120 for use in future routing operations. Access node1100 forwards the generated message 1410 to the network address of thehome session signaling server 1200 without forwarding the receivedregister message 1400. Thus, access node 1100 effectively intercepts1400 and sends message 1410 in its place. This Register messagesubstitution operation is transparent to Mobile node X which sent theoriginal Register message 1400 directed to its home session signalingserver 1200.

In response to receiving Register message 1410, home session signalingserver 1200 checks the record field of message 1410 and searches itsstate information 1201 for a matching record. The matching operation isperformed based on, e.g., all or a portion of the address included inthe Register message's register field which identifies the deviceattempting to register its location information. If a matching record isfound, the record is updated with the new forwarding informationincluded in the contact field of the message. In one embodiment of thepresent invention, if a matching record is not found, a new record iscreated. Resultant state information in 1201 and 1120 generated andstored in the access node and the home session signaling server,respectively, based on the exemplary messages shown in Table 1 isillustrated in Table 2 which is set forth below.

TABLE 2 STATE INFORMATION Element Record Forward Address Home User= userof ENx User= Home Session Signaling Session address of ENx (User=user ofSignaling ENx, Domain=domain of HSSSN) Server Domain= domain of HSSSNDomain= Network Address of State 1201 access node 1100 Example: Example:ENx@Home1.com ENx%Home1.com@20.0.0.1 Access Node User= Home SessionNetwork address of directly State Signaling address of connected ENxInformation ENx (User=user of ENx, 1120 Domain=domain of HSSSN) Domain=Network Address of access node 1100 Example: Example:ENx%Home1.com@20.0.0.1 10.0.0.1

In an alternative embodiment of the present invention, which alsoresults in the transmission of two register messages 1400, 1410 as shownin FIG. 9, End Node X 1002 is aware of the session signaling servermodule 1110 in access node 1100. End node X 1002 sends a REGISTERmessage 1400 directly to the network address of the access node 1100. Insuch an embodiment, register message 1400 will include the address ofthe access node in the Target field of the message and not the addressof the home session signaling server. Table 3 shows the Register message1400 which will be generated in such an embodiment in the first row ofthe table and the Register message 1410 which will be generated by theaccess n ode 1100 in the second row.

TABLE 3 REGISTER MESSAGE CONTENT MESSAGE Target Record Contact MessageHome Session Home Session Forwarding Session 1400 Signaling ServerSignaling Address of Signaling Address of ENx from MN Address ENxaddressed User= NULL User= user of ENx User= Home Session to ANSignaling address of ENx (User=user of ENx, Domain=domain of HSSSN)Domain= domain of Domain= domain of Domain= Network Address of HSSSNHSSSN access node 1100 Example: Example: Example: Home1.comENx@Home1.com ENx%Home1.com@20.0.0.1 AN Home Session Home SessionForwarding Session inspects, Signaling Server Signaling Address ofSignaling Address of ENx keeps state Address ENx and User= NULL User=user of ENx User= Home Session forwards Signaling address of ENx message(User=user of ENx, 1410 as is Domain=domain of HSSSN) to HSSSN Domain=domain of Domain= domain of Domain= Network Address of HSSSN HSSSNaccess node 1100 Example: Example: Example: Home1.com Home1.comENx%Home1.com@20.0.0.1

The REGISTER message 1400 (shown in Table 3) includes the access node's1100 network address. In one embodiment of this invention, as part ofthe processing performed by the access node's session signaling servermodule 1110 in response to receiving the Register message address to theaccess node 1100, the contact field is translated to a session signalingaddress resulting from the amendment of the access node's 1100 networkaddress to the end node X 1002 session signaling address. The exemplarymessage 1410 resulting from such processing is shown in the second rowto Table 3. It is this message which is transmitted to the home sessionsignaling server 1200. The home session signaling server 1200 willprocesses the received message in the same manner as previouslydiscussed with regard to the Table 2 example. The resultant state in1201 and 1120 in this example will be identical to that of Table 2.

FIG. 10 illustrates a simplified version of the exemplary system 1000 ofFIG. 7 and depicts session signaling performed as part of the processesof an aggregated registration of the forwarding address of end node X1002 to a two home session signaling server 1200, 1200′ via access node1100. The message processing involves a Register message broadcastoperation performed by access node 1100 in accordance with an embodimentof the present invention. In the FIG. 10 example, the methods ofprocessing and transmitting register messages described above in regardto FIG. 9 are applied to the transmission of registration informationfrom an access node to a plurality of home session signaling serverswithout the need for the end node 1002 to transmit multiple registrationmessages, one per home session signaling server in which registrationinformation is to be stored. This embodiment offers the advantage ofefficiently using radio bandwidth, a valuable resource, which is used tocommunicate register messages between end node 1002 and access node1100. It does this by allowing one register message 1420 to serve thepurpose of multiple messages.

Table 4 shows the aggregated Register message 1420 which will begenerated in such an embodiment in the first row of the table and theindividual Register messages 1430 and 1440 which will be generated bythe access node 1100 in the second row and third row respectively.

The REGISTER message 1400 (shown in Table 3) includes the access node's1100 network address in the contact field. It also includes in thenrecord field both of the addresses of the end node X 1002 thatcorrespond to the home session signaling servers 1200 and 1200′. In oneembodiment of this invention, as part of the processing performed by theaccess node's session signaling server module 1110 in response toreceiving the Register message with multiple addresses in the recordfield, two individual messages are generated, one for each address. TheREGISTER message 1430 is shown in the second row of Table 4 and includesthe address of End Node X 1002 corresponding to the home sessionsignaling server 1200 in the record field. The REGISTER message 1440 isshown in the third row of Table 4 and includes the address of End Node X1002 corresponding to the home session signaling 1200′ in the recordfield. For each of the REGISTER messages 1430, 1440 the contact fieldincludes a concatenation of the End Node's X 1002 address from thecorresponding home session signaling servers 1200 or 1200′ and theaddress of the access node 1100, which makes the identifiers unique inboth the home session signaling server state 1201, 1201′ and in theaccess node state 1120.

FIG. 14 illustrates an exemplary register message 1420. As shown in FIG.14, the exemplary message 1420 includes three separate fields, a targetfield 1422, a contact field 1424 and a record field 1426. The recordfield further includes at least two end node session signalingidentifiers, e.g. end node session signaling identifier 1 1428 and endnode session signaling identifier 2 1429. Table 4 shown below, furtherillustrates the exemplary contents of the three fields of an exemplaryRegister message 1420.

TABLE 4 REGISTER MESSAGE CONTENT MESSAGE Target Record Contact MessageHome Session Home Session Signaling Forwarding Session Signaling 1420Signaling Server Address 1 of ENx Address of ENx from MN Addressaddressed User= NULL User= user of ENx User= user of ENx to AN Domain=domain of Domain= domain of Domain= Network Address of HSSSN HSSSN1access node 1100 Example: Example: Example: Home1.com ENx@Home1.comENx@20.0.0.1 Home Session Signaling Address 2 of ENx User= user of ENx1002 Domain= domain of HSSSN2 Example: ENx@Home2.com Message HomeSession Home Session Signaling Forwarding Session Signaling 1430Signaling Server 1 Address 1 of ENx Address of ENx from AN Addressaddressed User= NULL User= user of ENx User= Home Session Signaling toHSSSN 1 address 1 of ENx (User=user of ENx, Domain=domain of HSSSN1)Domain= domain of Domain= domain of Domain= Network Address of HSSSN1HSSSN1 access node 1100 Example: Example: Example: Home1.comENx@Home1.com ENx%Home1.com@20.0.0.1 Message Home Session Home SessionSignaling Forwarding Session Signaling 1440 Signaling Server 2 Address 2of ENx Address 2 of ENx From AN Address addressed User= NULL User= userof ENx User= Home Session Signaling to HSSSN 2 address of ENx (User=userof ENx, Domain=domain of HSSSN2) Domain= domain of Domain= domain ofDomain= Network Address of HSSSN2 HSSSN2 access node 1100 Example:Example: Example: Home2.com ENx@Home2.com ENx%Home2.com@20.0.0.1

Table 5 illustrates the state information obtained by the home sessionsignaling servers 1201, 1201′ in the first and second row respectivelyand the access node state information 1120 in the third row. The latterincludes two sub-records, one for each address of End Node X 1002, bothpointing to the same directly connected network address of End Node X inthe forwarding address.

TABLE 5 STATE INFORMATION Element Record Forwarding Address Home User=user of ENx User= Home Session Signaling Session address 1 of ENx(User=user of Signaling ENx, Domain=domain of HSSSN1) Server 1 Domain=domain of Domain= Network Address of access State 1201 HSSSN1 node 1100Example: Example: Home2.com ENx%Home2.com@20.0.0.1 Home User= user ofENx User= Home Session Signaling Session address 2 of ENx (User=user ofSignaling ENx, Domain=domain of HSSSN2) Server 2 Domain= domain ofDomain= Network Address of access State 1201′ HSSSN2 node 1100 Example:Example: Home2.com ENx%Home2.com@20.0.0.1 Access Node User= Home SessionNetwork address of directly State Signaling address 1 of connected ENxInformation ENx (User=user of ENx, 1120 Domain=domain of HSSSN1) Domain=Network Address of access node 1100 Example: Example:ENx%Home1.com@20.0.0.1 10.0.0.1 AND User= Home Session Signaling address2 of ENx (User=user of ENx, Domain=domain of HSSSN2) Domain= NetworkAddress of access node 1100 Examp1e: ENx%Home2.com@20.0.0.1

In alternative embodiments of the present invention an End node X 1002registers with a plurality of home session signaling servers and notjust two. The same aggregated registration method given in the exampleabove is used for that purpose.

FIG. 11 illustrates a simplified version of the exemplary system 2002 ofFIG. 8 and depicts session signaling performed as part of the processesof a chained registration of the forwarding address of end node X 1002to a paging and location server 1300 and a home session signaling server1200 via access node 1100. In accordance with a first signaling methodof the present invention end node X 1002 is not aware of the presence ofthe proxy and location server 1300 or the signaling server module 1110in the access node 1100. The signaling associated with such anembodiment is shown in FIG. 11.

In the FIG. 11 embodiment, in order to register its location with itsHome session signaling server 1200, end node X 1002 sends a REGISTERmessage 1500 directed to the network address of the home sessionsignaling server node 1200. Since the access node serves as the mobilenode's point of network attachment, this message is routed throughaccess node 1100 where it is processed. In one embodiment, the sessionsignaling server module 1110 modifies the received message 1500 byperforming a translation operation to the contact field of the receivedmessage 1500 changing its value to a value that includes the accessnode's 1100 network address. In one particular embodiment, the contactfield is translated to become a session signaling address that is theresult of amending the access node's 1100 network address to the sessionsignaling address of end node X 1002.

In accordance with the present invention, Paging and Location Server1300 monitors for messages sent to it and, in response to detecting sucha message intercepts and processes the message. In particular the Pagingand Location Server 1390 processes the received message to generate oneor more new Register messages there from. The Server 1300 also storesrelevant address information in its set of State information 1301.

In accordance with the embodiment shown in FIG. 11, the paging andlocation server 1300 generates and transmits a new register message 1520to the home session signaling server 1200. In one embodiment, the pagingand location server 1300 modifies the received message 1510 byperforming a translation operation to the contact field of the receivedmessage 1510 changing its value to a value that includes the sessionsignaling address of the paging and location server 1300. In oneparticular embodiment, the contact field is translated to become asession signaling address that is the result of amending the sessionsignaling address of the paging and location server 1300 to the sessionsignaling address of end node X 1002.

TABLE 6 REGISTER MESSAGE CONTENT MESSAGE Target Record Contact MessageHome Session Home Session Signaling Forwarding Session Signaling 1500Signaling Server Address of ENx Address of ENx with domain from ENxAddress part equal to network addressed address of ENx to HSSSN User=NULL User= user of ENx User= user of ENx Domain= domain of Domain=domain of Domain= Network Address of HSSSN HSSSN ENx Example: Example:Example: Home1.com Home1.com ENx@10.0.0.1 AN Home Session Home SessionSignaling Forwarding Session Signaling Intercepts, Signaling ServerAddress of ENx Address of ENx Modifies Address Contact User= NULL User=user of ENx User= Home Session Signaling field and address of ENx(User=user forwards of ENx, Domain=domain of message HSSSN) 1510 Domain=domain of Domain= domain of Domain= Network Address of addressed HSSSNHSSSN access node 1100 to PLS Example: Example: Example: Home1.comHome1.com ENx%Home1.com@20.0.0.1 PLS Home Session Home Session SignalingForwarding Session Signaling Modifies Signaling Server Address of ENxAddress of ENx Contact Address field and User= NULL User= user of ENxUser= Home Session Signaling forwards address of ENx (User=user messageof ENx, Domain=domain of 1520 HSSSN) addressed Domain= domain of Domain=domain of Domain=domain of PLS to HSSSN HSSSN HSSSN Example: Example:Example: Home1.com Home1.com ENx%Home1.com@PLS.com

Table 6 shows the aggregated Register message 1500 which will begenerated in such an embodiment in the first row of the table and theRegister messages 1510 and 1520 which will be generated by the accessnode 1100 and the paging and location server 1300 in the second row andthird row respectively.

The REGISTER message 1500 (shown in Table 6) includes the home sessionsignaling server 1200 address in the Target field, the session signalingaddress of the End Node X 1002 in the Record field and network addressof the End Node X 1002 in the contact field. In one embodiment of thisinvention, as part of the processing performed by the access node'ssession signaling server module 1110 in response to intercepting theRegister message, the contact field is translated to a session signalingaddress resulting from the amendment of the access node's 1100 networkaddress to the end node X 1002 session signaling address. The exemplarymessage 1510 resulting from such processing is shown in the second rowto Table 6. It is this message which is transmitted to the paging andlocation server 1300.

In one embodiment of this invention, as part of the processing performedby the paging and location server 1300 in response to receiving theRegister message, the contact field is translated once more to a sessionsignaling address resulting from the amendment of the session signalingaddress of the paging and location server 1300 to the end node X 1002session signaling address. The exemplary message 1520 resulting fromsuch processing is shown in the third row to Table 6. It is this messagewhich is transmitted to the paging and location server 1300. The homesession signaling server 1200 will processes the received message in thesame manner as previously discussed with regard to the Table 2 example.The resultant state in 1201, 1301 and 1120 in this example isillustrated in Table 7. As a result the home session signaling server1201 will forward any incoming signaling for End Node X 1002 to thepaging and location server 1300, which in its turn will forward it tothe access node 1100 before being delivered to the End Node X itself.

TABLE 7 STATE INFORMATION Element Record Forwarding Address Home User=user of ENx User= Home Session Signaling Session address of ENx(User=user of Signaling ENx, Domain=domain of HSSSN) Server Domain=domain of Domain= domain of PLS State 1201 HSSSN Examp1e: Example:ENx@Home1.com ENx%Home1.com@PLS.com PLS State User= Home Session User=Home Session Signaling 1301 Signaling address of address of ENx(User=user of ENx (User=user of ENx, ENx, Domain=domain of HSSSN)Domain=domain of HSSSN) Domain= domain of PLS Domain=Network Address ofaccess node 1100 Example: Example: ENx%Home1.com@PLS.comENx%Home1.com@20.0.0.1 Access Node User= Home Session Network address ofdirectly State Signaling address of connected ENx Information ENx(User=user of ENx, 1120 Domain=domain of HSSSN) Domain= Network Addressof access node 1100 Example: Example: ENx%Home1.com@20.0.0.1 10.0.0.1

In accordance with a second signaling method of the present inventionend node X 1002 is aware of the presence of the proxy and locationserver 1300 and the signaling server module 1110 in the access node1100. The signaling associated with such an embodiment is illustrated inFIG. 12.

In the FIG. 12 embodiment, in order to register its location with itsHome session signaling server 1200, end node X 1002 sends a REGISTERmessage 1600 directed to the network address of the access node 1100.Said message includes the session signaling address of the paging andlocation server 1300 in the Target field. The Record field is comprisedby an end node X 1002 identifier concatenated with the session signalingaddress of the paging and location server 1300; this address will now bereferred to as the paging and location address of the end node X 1002.In one embodiment of this invention the end node X 1002 identifier isthe home session signaling address of the end node X 1002. The contactfield includes the same end node X 1002 identifier user in the Recordfield concatenated by the access node 1100 network address.

The session signaling server module 1110 of said access node receivesand processes the message; stores relevant address information in itsset of State information 1120 and forwards the message 1610 as is to thepaging and location server 1300. In accordance with the presentinvention, Paging and Location Server 1300 monitors for messages sent toit and, in response to detecting such a message intercepts and processesthe message. In particular the Paging and Location Server 1300 storesrelevant address information in its set of State information 1301.

In parallel, as depicted in the FIG. 12 embodiment, end node X 1002 alsosends a REGISTER message 1620 directed to the home session signalingserver 1200. Said message includes the session signaling address of thehome session signaling server 1200 in the Target field and the sessionsignaling address of the end node X 1002 in the record field. In oneparticular embodiment, the contact contains a session signaling addressthat is the result of amending the session signaling address of thepaging and location server 1300 to the session signaling address of endnode X 1002 in the paging and location server 1300.

Table 8 shows the messages 1600, 1610 and 1620 generated in such anembodiment in the first, second and third row of the table.

TABLE 8 REGISTER MESSAGE CONTENT MESSAGE Target Record Contact MessagePLS Address PLS Session Signaling Forwarding Session Signaling 1600Address of ENx Address of ENx from ENx User= NULL User= User of ENx inUser= user of ENx in PLS addressed PLS to AN Domain= domain Domain=domain of PLS Domain= Network Address of of PLS access node 1100Example: Example: Example: PLS.com ENx%Home1.com@PLS.comENx%Home1.com@20.0.0.1 AN keeps PLS Address PLS Session SignalingForwarding Session Signaling state and Address of ENx Address of ENxforwards User= NULL User= user of ENx in User= user of ENx in PLSmessage PLS 1610 Domain= domain Domain= domain of Domain= NetworkAddress of addressed of PLS PLS access node 1100 to PLS Example:Example: Example: PLS.com ENx@PLS.com ENx%Home1.com@20.0.0.1 MessageHome Session Home Session Forwarding Session Signaling 1620 SignalingServer Signaling Address of Address of ENx from ENx Address ENxaddressed User= NULL User= user of ENx User= user of ENx in PLS to HSSSNDomain= domain Domain= domain of Domain=domain of PLS of HSSSN HSSSNExample: Example: Example: Home1.com ENx@Home1.com ENx%Home1.com@PLS.com

The resultant state in 1201, 1301 and 1120 in this example isillustrated in Table 9. As with the state illustrated in FIG. 7 as aresult the home session signaling server 1201 will forward any incomingsignaling for End Node X 1002 to the paging and location server 1300,which in its turn will forward it to the access node 1100 before beingdelivered to the End Node X itself, it is now done, however, withoutneed for message interception and translation but only by normal messagereception and processing.

TABLE 9 STATE INFORMATION Element Record Forwarding Address Home User=user of ENx User= user of ENx in PLS Session Domain= domain of Domain=domain of PLS Signaling HSSSN Server Example: Example: State 1201ENx@Home1.com ENx%Home1.com@PLS.com PLS State User= user of ENx in User=user of ENx in PLS 1301 PLS Domain= domain of PLS Domain= NetworkAddress of access node 1100 Example: Example: ENx%Home1.com@PLS .comENx%Home1.com@20.0.0.1 Access Node User= user of ENx in Network addressof directly State PLS connected ENx Information Domain= Network 1120Address of access node 1100 Example: Example: ENx%Home1.com@20.0.0.110.0.0.1

FIG. 13 illustrates a simplified version of the exemplary system 2002 ofFIG. 8 and depicts session signaling performed as part of the processesof a handoff. In this example the end node X 1002 is moving from accessnode 1100 to access node 1100′. End node X 1002 registers its relocationso that incoming signaling will reach it at its correct location whichnow is access node 1100′. To that end the end node X 1002 performs aregistration equivalent to paging and location server 1300 registrationalready illustrated by messages 1600, 1610 in FIG. 12 sends REGISTERmessage 1630 to the network address of access node 1100′. Registrationwith the home session signaling server 1200 (of FIG. 12) is not requiredin this case since the said server 1200 correctly forwards any incomingsignaling to the paging and location server 1300 based on current stateinformation 1201 (of FIG. 12). The same would apply in the case ofaggregated registration as depicted in FIG. 10 i.e.: the existence of apaging and location server in the visited domain eliminates the need formultiple registrations to multiple home session signaling servers.

In the FIG. 13 embodiment, in order to updates its registered locationwith its paging and location server 1300, end node X 1002 sends aREGISTER message 1630 directed to the network address of the access node1100′. Said message is similar to message 1600 of (FIG. 12). Thedifference is that the contact field includes the end node X 1002identifier used in the Record field concatenated by the access node1100′ network address instead of the access node 1100 network address.

The session signaling server module 1110 of said access node receivesand processes the message; stores relevant address information in itsset of State information 1120. and forwards the message 1640 as is tothe paging and location server 1300. In accordance with the presentinvention, Paging and Location Server 1300 monitors for messages sent toit and, in response to detecting such a message intercepts and processesthe message. In particular the Paging and Location Server 1300 storesrelevant address information in its set of State information 1301.

TABLE 10 REGISTER MESSAGE CONTENT MESSAGE Target Record Contact MessagePLS Address PLS Session Signaling Forwarding Session Signaling 1630Address of ENx Address of ENx from ENx User= NULL User= User of ENx inUser= user of ENx in PLS addressed PLS to AN Domain= domain of Domain=domain of PLS Domain= Network Address of PLS access node 1100′ Example:Example: Example: PLS.com ENx%Home1.com@PLS ENx%Home1.com@20.0.1.1 ANkeeps PLS Address PLS Session Signaling Forwarding Session Signalingstate and Address of ENx Address of ENx forwards User= NULL User= userof ENx in User= user of ENx in PLS message PLS 1640 Domain= domain ofDomain= domain of Domain= Network Address of addressed PLS PLS accessnode 1100′ to PLS Example: Example: Example: PLS.comENx%Home1.com@PLS.com ENx%Home1.com@20.0.1.1The result is updated state information in access node 1100′ and pagingand location server 1300. That state is depicted in Table 11.

TABLE 11 STATE INFORMATION Element Record Forwarding Address PLS StateUser= user of ENx in User= user of ENx in PLS 1301 PLS Domain= domain ofPLS Domain= Network Address of access node 1100′ Example: Example:ENx%Home1.com@PLS.com ENx%Home1.com@20.0.1.1 Access Node User= user ofENx in Network address of directly State PLs connected ENx InformationDomain= Network 1120′ Address of access node 1100′ Example: Example:ENx%Home1.com@20.0.1.1 10.0.0.1

Numerous variations on the above-described inventions will be apparentto those of ordinary skill in the art based on the above description.Such variations are to be considered within the scope of the invention.

1. A communications method, comprising the steps of: operating a homesession signaling server node to receive a first registration messageincluding an end node session signaling address, said end node sessionsignaling address being a session signaling address of a mobile node,and an access node session signaling address, said access node sessionsignaling address being a session signaling address of an access nodewhich is a base station that includes a session signaling server module;and operating the home session signaling server node to storeregistration information associating said access node session signalingaddress with said end node session signaling address.
 2. The method ofclaim 1, wherein said base station includes a receiver for receivingsignals transmitted by said mobile node through a wirelesscommunications channel and a transmitter for transmitting signals overthe air to said mobile node.
 3. The method of claim 2, furthercomprising: operating the receiver in the access node to receive asecond registration message from said mobile node.
 4. The method ofclaim 3, further comprising: operating the session signaling module inthe access node to perform a forwarding address translation operation togenerate said first registration message from said second registrationmessage.
 5. The method of claim 4, wherein said second registrationmessage includes multiple session signaling server destinationaddresses.
 6. The method of claim 5, further comprising: operating saidaccess node to generate a plurality of registration messages from thesecond registration message received from said end node, the firstregistration message being one of said plurality of generatedregistration messages.
 7. The method of claim 6, wherein at least oneregistration message is generated by the access node for each of themultiple session signaling server destination addresses included in thesecond registration message.
 8. The method of claim 7, wherein each ofsaid plurality of registration messages generated by said access nodeincludes a different destination address obtained from the registrationmessage received from said end node.
 9. The method of claim 3, whereinthe second registration message received from said end node is addressedto said home session signaling server node.
 10. The method of claim 3,wherein said second registration message includes multiple sessionsignaling server destination addresses.
 11. The method of claim 10,further comprising: operating said access node to generate a pluralityof registration messages from the second registration message receivedfrom said end node, the first registration message being one of saidplurality of generated registration messages.
 12. The method of claim11, wherein at least one registration message is generated by the accessnode for each of the multiple session signaling server destinationaddresses included in the second registration message.
 13. The method ofclaim 12, wherein each of said plurality of registration messagesgenerated by said access node includes a different destination addressobtained from the registration message received from said end node. 14.A communications method, comprising the steps of: operating a homesession signaling server node to receive a first registration messageincluding an end node session signaling address, said end node sessionsignaling address being a session signaling address of a mobile node,and an access node session signaling address, said access node sessionsignaling address being a session signaling address of an access nodewhich is a base station that includes a session signaling server module,said base station including a receiver for receiving signals transmittedby said mobile node through a wireless communications channel and atransmitter for transmitting signals over the air to the wirelessterminal; operating the home session signaling server node to storeregistration information associating said access node session signalingaddress with said end node session signaling address; operating thereceiver in the access node to receive a second registration messagefrom said end node; and operating the session signaling module in theaccess node to perform a forwarding address translation operation togenerate said first registration message from said second registrationmessage; and wherein performing a forwarding address translationoperation includes replacing at least a portion of an end node sessionsignaling address included in said second registration message with atleast a portion of the access node session signaling address, the accessnode session signaling address being included in a forwarding addressfield of the first registration message generated by said forwardingaddress translation.
 15. The method of claim 14, wherein the replacedportion of an end node session signaling address is a domain part ofsaid end node session signaling address.
 16. A communications systemcomprising: a home session signaling server including: means forreceiving registration messages including an end node session signalingaddress corresponding to a mobile node and an access node sessionsignaling address corresponding to an access node which is a basestation; and a memory for storing registration information associatingsaid access node session signaling address with said end node sessionsignaling address included in received registration messages.
 17. Thecommunication system of claim 16, further comprising: said access nodeincluding a session signaling server module and a wireless transmitterfor transmitting signals to said mobile node.
 18. The communicationsystem of claim 16, wherein said access node includes a messagegeneration module enabled to generate a plurality of session signalingregistration messages from a single session signaling registrationmessage received from the mobile node.
 19. The communication system ofclaim 16, wherein said access node further includes: transmissioncircuitry for transmitting each of said plurality of generated sessionsignaling registration messages to a different home session signalingserver.
 20. The communication system of claim 19 wherein said singlesession signaling registration message includes the address of multipledestination home session signaling servers.
 21. A communications systemcomprising: an access node which is a base station, said access nodeincluding a session signaling server module and a wireless transmitterfor transmitting signals to a mobile node, said session signaling servermodule including means for performing a forwarding address translationoperation to generate a second registration message from a firstregistration message received from an end node, said forwarding addresstranslation operation including substituting at least a portion of anend node session signaling address for at least a portion of an accessnode session signaling address included in the first registrationmessage, the access node session signaling address being included in aforwarding address field of the first registration message; a homesession signaling server including: i) a receiver module for receivingregistration messages including the end node session signaling addresscorresponding to the mobile node and the access node session signalingaddress corresponding to said access node which is the base station; andii) a memory for storing registration information associating saidaccess node session signaling address with said end node sessionsignaling address included in received registration messages.
 22. Amethod of operating a base station to process a first session signalregistration message from an end node, the method comprising: performingin the base station a forwarding address translation operation on saidfirst session signaling registration message to generate a secondsession signaling registration message; and transmitting said secondsession signaling message to another node.
 23. A method of operating anaccess node to process a first session signal registration message froman end node, the method comprising: performing a forwarding addresstranslation operation on said first session signaling registrationmessage to generate a second session signaling registration message; andtransmitting said second session signaling message to another node;wherein said access node is a base station which includes a receiver forreceiving signals transmitted to said access node over the air; andwherein performing a forwarding address translation operation includesreplacing at least a portion of an end node session signaling addresswith at least a portion of an access node session signaling address,said portion of the access node session signaling address being includedin a forwarding address field of the second registration message. 24.The method of claim 23, wherein the replaced portion of an end nodesession signaling address is a domain part of said end node sessionsignaling address.
 25. The method of claim 23, wherein said firstregistration message includes multiple session signaling serverdestination addresses.
 26. The method of claim 25, further comprising:generating a plurality of registration messages from the firstregistration message, the second registration message being one of saidplurality of generated registration messages.
 27. The method of claim26, wherein at least one registration message is generated by the accessnode for each of the multiple session signaling server destinationaddresses included in the second registration message.
 28. Acommunications apparatus, comprising: a module for generating a sessionsignaling register message including: a target field; a contact field;and at least two different end node session signaling identifiersbelonging to the same end node and being in addition to said targetfield and said contact field; and a transmitter for transmitting saidgenerated message.
 29. The apparatus of claim 28, wherein the twodifferent end node session signaling identifiers are first and secondsession signaling addresses corresponding to the same end node.
 30. Theapparatus of claim 29, wherein the first session signaling address isthe address of the end node in a first domain and wherein the secondsession signaling address is the address of the end node in a seconddomain.
 31. The apparatus of claim 29, wherein the contact fieldincludes a first address; wherein the target field includes a secondaddress; and wherein said at least two different end node sessionsignaling identifiers are in addition to said first and secondaddresses.
 32. The apparatus of claim 31, wherein the end node is amobile node; wherein a portion of said first session signaling addressidentifies a first target; and wherein a portion of said second sessionsignaling address identifies a second target.
 33. The apparatus of claim29, wherein said contact field includes a single session signalingaddress corresponding to the current location of the end node.
 34. Theapparatus of claim 29, wherein each session signaling address in saidregister message includes a user part and a domain part.
 35. Acommunications apparatus, comprising: a module for generating a sessionsignaling register message including: a target field; a contact field;and at least two different end node session signaling identifiers;wherein the two different end node session signaling identifiers arefirst and second session signaling addresses corresponding to the sameend node; wherein the first session signaling address is the address ofthe end node in a first domain and wherein the second session signalingaddress is the address of the end node in a second domain; wherein aportion of said first session signaling address identifies a firsttarget; and wherein a portion of said second session signaling addressidentifies a second target; wherein said first portion is the sessionsignaling address of a first home session signaling server; and whereinsaid second portion is the session signaling address of a second homesession signaling server; and a transmitter for transmitting saidgenerated message.
 36. A communications apparatus, comprising: a modulefor generating a session signaling register message including: a targetfield; a contact field; and at least two different end node sessionsignaling identifiers belonging to the same end node and being inaddition to said target field and said contact field; and a transmitterfor transmitting said generated message; wherein the two different endnode session signaling identifiers are first and second sessionsignaling addresses corresponding to the same end node; and wherein saidtarget field includes a NULL value.
 37. A communications apparatus,comprising: a module for generating a session signaling register messageincluding: a target field; a contact field; and a record field includingat least two different end node session signaling identifiers; whereinthe two different end node session signaling identifiers are first andsecond session signaling addresses corresponding to the same end node;and wherein said target field includes at least two different sessionsignaling addresses, each one of the different session signalingaddresses in the target field corresponding to a single one of saidaddresses in the record field, the target and record fields eachincluding the same number of session signaling addresses; and atransmitter for transmitting said generated message.
 38. Acommunications method, the method comprising: operating a mobile nodeto: i) generate a session signaling register message including: a targetfield; a contact field; and at least two different end node sessionsignaling identifiers corresponding to said mobile node in addition tosaid target field and said contract field; and ii) transmit saidgenerated session signaling register message to a base station over awireless communications channel.
 39. The method of claim 38, wherein thetwo different end node session signaling identifiers are first andsecond session signaling addresses corresponding to the same mobilenode.
 40. The method of claim 39 wherein the first session signalingaddress is the address of the end node in a first domain and wherein thesecond session signaling address is the address of the end node in asecond domain.
 41. The method of claim 39, wherein said contact fieldincludes a single session signaling address corresponding to the currentlocation of the end node.
 42. The method of claim 39, wherein eachsession signaling address in said register message includes a user partand a domain part.
 43. A communications method, the method comprising:operating a mobile node to: i) generate a session signaling registermessage including: a target field; a contact field; and at least twodifferent end node session signaling identifiers corresponding to saidmobile node, said at least two different end node session signalingidentifiers being in addition to said target field and said contractfield; and ii) transmit said generated session signaling registermessage to a base station over a wireless communications channel;operating a receiver in said base station to: i) receive saidtransmitted session signaling register message; ii) to perform anaddress translation operation thereon to generate another sessionsignaling register message; and iii) transmit said another sessionsignaling register message to another node over a second communicationslink which is not a wireless communications link.
 44. A communicationsmethod, the method comprising: operating a mobile node to: i) generate asession signaling register message including: a target field; a contactfield; and at least two different end node session signaling identifierscorresponding to said mobile node; and ii) transmit said generatedsession signaling register message to a base station over a wirelesscommunications channel; wherein the two different end node sessionsignaling identifiers are first and second session signaling addressescorresponding to said mobile node; wherein the first session signalingaddress is the address of said end node in a first domain and whereinthe second session signaling address is the address of said end node ina second domain; wherein a portion of said first session signalingaddress identifies a first target; and wherein a portion of said secondsession signaling address identifies a second target.
 45. Acommunications method, the method comprising: operating a mobile nodeto: i) generate a session signaling register message including: a targetfield; a contact field; and at least two different end node sessionsignaling identifiers corresponding to said mobile node; and ii)transmit said generated session signaling register message to a basestation over a wireless communications channel; wherein the twodifferent end node session signaling identifiers are first and secondsession signaling addresses corresponding to said mobile node; whereinthe first session signaling address is the address of said end node in afirst domain and wherein the second session signaling address is theaddress of said end node in a second domain; wherein a portion of saidfirst session signaling address identifies a first target; and wherein aportion of said second session signaling address identifies a secondtarget; wherein said first portion is the session signaling address of afirst home session signaling server; and wherein said second portion isthe session signaling address of a second home session signaling server.46. A communications method, the method comprising: operating a mobilenode to: i) generate a session signaling register message including: atarget field; a contact field; and at least two different end nodesession signaling identifiers corresponding to said mobile node; and ii)transmit said generated session signaling register message to a basestation over a wireless communications channel; wherein the twodifferent end node session signaling identifiers are first and secondsession signaling addresses corresponding to the same mobile node; andwherein said target field includes a NULL value.
 47. A communicationsmethod, the method comprising: operating a mobile node to: i) generate asession signaling register message including: a target field; a contactfield; and a record field including at least two different end nodesession signaling identifiers corresponding to said mobile node; and ii)transmit said generated session signaling register message to a basestation over a wireless communications channel; wherein the twodifferent end node session signaling identifiers are first and secondsession signaling addresses corresponding to said mobile node; andwherein said target field includes at least two different sessionsignaling addresses, each one of the different session signalingaddresses in the target field corresponding to a single one of saidaddresses in the record field, the target and record fields eachincluding the same number of session signaling addresses.
 48. Acommunications apparatus, comprising: a module for generating a sessionsignaling register message including: a target field; a contact field;and at least two different end node session signaling identifiersbelonging to the same end node and being in addition to said targetfield and said contact field; and a transmitter for transmitting saidgenerated message; wherein said two different end node session signalingidentifiers are included in a record field which is in addition to saidtarget field and contact field; wherein the two different end nodesession signaling identifiers are first and second session signalingaddresses corresponding to the same end node; and wherein the first endnode session signaling address includes at least a user portion and adomain portion, said user portion including characters identifying auser, said domain portion including characters identifying a networkdomain.
 49. The apparatus of claim 48, wherein the user portion anddomain portion of said first end node session signaling address eachinclude alphanumeric characters, said user portion and domain portionbeing separated by an @ symbol.
 50. The apparatus of claim 49, whereinthe second end node session signaling address includes at least a userportion and a domain portion, said user portion including alphanumericcharacters identifying said user, said domain portion includingalphanumeric characters identifying a network domain.
 51. Acommunications method, the method comprising: operating a mobile nodeto: i) generate a session signaling register message including: a targetfield; a contact field; and at least two different end node sessionsignaling identifiers corresponding to said mobile node, said at leasttwo different end node session signaling identifiers being in additionto said target field and said contract field; and ii) transmit saidgenerated session signaling register message to a base station over awireless communications channel; wherein said two different end nodesession signaling identifiers are included in a record field which is inaddition to said target field and contact field; wherein the twodifferent end node session signaling identifiers are first and secondsession signaling addresses corresponding to the same end node; andwherein the first end node session signaling address includes at least auser portion and a domain portion, said user portion includingcharacters identifying a user, said domain portion including charactersidentifying a network domain.
 52. The method of claim 51, wherein theuser portion and domain portion of said first end node session signalingaddress each include alphanumeric characters, said user portion anddomain portion being separated by an @ symbol.
 53. The method of claim52, wherein the second end node session signaling address includes atleast a user portion and a domain portion, said user portion includingalphanumeric characters identifying said user, said domain portionincluding alphanumeric characters identifying a network domain.
 54. Acommunications apparatus, comprising: a receiver for receiving a sessionsignaling register message including: a target field; a contact field;and at least two different end node session signaling identifiersbelonging to the same end node and being in addition to said targetfield and said contact field; and a module for processing said receivedsession signaling register message.
 55. A communications apparatus,comprising: a module for generating a session signaling register messageincluding: a target field; a contact field; at least two different endnode session signaling identifiers belonging to the same end node andbeing in addition to said target field and said contact field; and atransmitter for transmitting said generated message; wherein the twodifferent end node session signaling identifiers are first and secondsession signaling addresses corresponding to the same end node; whereinsaid at least two different end node session signal identifiers areincluded in a third field of said message which is separate from saidtarget field and said contact field; and wherein a user part of thefirst session signaling address and a user part of the second sessionsignaling address are the same; wherein a domain part of the firstsession signaling address and a domain part of the second sessionsignaling addresses are different.
 56. The apparatus of claim 55,wherein said target field includes a home session signaling serveraddress; and wherein said contact field includes a forwarding sessionsignaling address including a user part which is the same as the userpart included in said first and second session signaling addresses. 57.A computer readable medium embodying computer executable instructionsfor implementing a method of operating a home session signaling node,the method comprising the steps of: operating the home session signalingserver node to receive a first registration message including an endnode session signaling address, said end node session signaling addressbeing a session signaling address of a mobile node, and an access nodesession signaling address, said access node session signaling addressbeing a session signaling address of an access node which is a basestation that includes a session signaling server module; and operatingthe home session signaling server node to store registration informationassociating said access node session signaling address with said endnode session signaling address.
 58. A home session signaling serverincluding: a receiver for receiving registration messages including anend node session signaling address corresponding to a mobile node and anaccess node session signaling address corresponding to an access nodewhich is a base station; and memory for storing registration informationassociating said access node session signaling address with said endnode session signaling address included in received registrationmessages.